Although there are numerous examples of prior art in this field, such as WO 2013/075675, the current invention overcomes major flaws that have prevented them from widespread use in the field of bicycles featuring large tires until now. Most of the current state of the art concentrates in making sure the tire is inflated to an adequate pre-selected pressure by:
Step 1: Acquiring air from the atmosphere and adding into the tire using a pump or similar mechanical device; or acquiring air from a pre-pressurized reservoir and adding it into the tire using valve or similar regulation device:
Step 2: If necessary, releasing back air into the atmosphere should the tire become over-inflated using a valve or similar regulation device.
Step 1 is by far the most complex and numerous designs to address it exist. These include piston-based valves inserted into the hub, rim or directly within the tire itself. These designs concentrate in achieving the pre-set minimal pressure while minimizing overall system weight, complexity and mechanical load to the rider. Moreover, this step is also implemented in numerous different designs in similar applications for cars, trucks, agricultural and industrial transport systems.
Step 2 is usually much simpler and in most cases only includes an air-release valve with a preset maximum tire pressure (placed in the rim or hub). In car and truck applications, a more complex system may exist with the ability to manage the pre-set maximum tire pressure while riding the vehicle, either by pure mechanical or electronically controlled means.
Modern bicycles, and in particular mountain bikes, have been incorporating increasingly large tires across the years, currently featuring tires with rim diameters of 622 mm or more and/or tire-width of 5″ or more. Although these large tires may seem inefficient and awkward to ride for those not versed in the state of the art, when set at relatively low pressures, they provide for much more energy efficient, controllable and comfortable riding over rugged terrain when compared to thin and high pressure tires. Moreover, these tires can be mounted in “tubeless” configuration, which prevents most flats and further allowing lower pressures.
However, the large tires and very low pressures make them relatively inefficient when riding over smooth terrain. To overcome this, a rider will need to increase the tire air pressure. Actually, the larger the tire, the more the pressure-efficiency balance between rugged and smooth terrain becomes sensitive, and in many circumstances, it is impossible to pre-set the tire at an ideal pressure given the typical mixed-terrain circuits where these mountain bikes are usually ridden.
Therefore, incorporation of a tire-pressure regulation device will be a priori extremely convenient in these mountain biking applications; however, none of the existing state of the art has achieved any significant usage in this fields because:
In mountain biking applications it is impractical to filter efficiently the incoming atmosphere air given the variety of riding circuits featuring large quantities of dust, dirt and mud;
It is impractical to incorporate reservoirs featuring large capacity of highly compressed air, and when these are incorporated, only a few full inflation cycles can be achieved given the relatively large size of the tires;
Alternative liquefied-CO2 based reservoirs have a similar cycle-limitation, and they are not compatible with most tubeless systems because CO2 “corrupts” the sealing properties of the dedicated sealing liquid incorporated inside these tires;
When existing, the mechanically-driven pumps apply mechanical load to the rider either continuously, or at the worst time in the ride, or without direct control of the rider;
The systems feature none or limited ability to determine set-tire-pressure without dismounting the bike.
DE 4010711 describes a closed system for application in all-terrain 4-wheeled motor vehicles and already addresses some of the limitations of other systems described in the previous art, namely the ability to control tire pressure without needing to refill air from the atmosphere or an external device. However, the document presents a high degree of mechanical load, it is very heavy as it unbalances the wheel, and it is wholly incompatible with current mountain bike frame, drive train and wheel technologies, and finally, it cannot be directly controlled via mechanical means.
US2004216827A1 describes a tire inflation and pressure maintaining system, whereas in one of its embodiments the step 1 mentioned above is based on a vane pump. However, the vane pump is configured such as the pump rotor is static with respect to the vehicle's main axle and therefore the pump operation cannot be controlled independently of the wheel's motion. This creates continuous mechanical load and it cannot be used as unique single control device to change the tire pressure at will. Also, the invention cannot be directly controlled remotely via mechanical means. And finally, due to the intended field of application, the described embodiments are also wholly incompatible with current mountain bike frame, drive train and wheel technologies.